% ALSO SEE % for other types of plots you can make

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3 Table of Contents work in class... 1 example 1 - using plot()... 1 example 2 - two or more curves on one plot... 4 example 3 - user written functions... 4 example 4 - image manipulation... 6 work in class % August 14th example 1 - using plot() % ALSO SEE % for other types of plots you can make a = linspace(0,2*pi,100); s = sin(a); figure(1) plot(s) title('plot(s) >> sin(a) vs. index # of array') % add a line with new figure number before each plot in a code % section so that all figures will appear when Published figure(2) plot(a,s) title('plot(a,s) >> sin(a) vs. a') figure(3) plot(a,s,'rx') title('plot(a,s,''rx'') >> use optional string to plot to get e.g., red x''s') % note use of double '' to get ' inside string figure(4) plot(a,s,'rx-') title('plot(a,s,''rx-'') >> use optional string to plot to get e.g., red x''s & line') % can also add y and x axis labels ylabel('sin(a)') xlabel('a') 1

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6 example 2 - two or more curves on one plot % workspace still has a and s from above % add line "clear all" here to clear workspace if you need to % or "clear s" if you just want to clear one variable, s here c = cos(a) + 1; % now plot two curves on same plot and same axes plot(a,s,a,c,'b.') title('plot(a,s,a,c,''b.'') >> two curves on same plot and same axes') % optionally use axis() to set the range of the axes axis([0 2*pi -1 max(c)+1]) % see plotyy() if want different left y and right y axes for % plotting variables with very different numeric ranges example 3 - user written functions % Matlab has standard functions such as sin and cos % you can write your own functions % your functions will be written in an m-file with the same % name as your function 4

7 % why write your own functions? % (1) break a long program into modules which are easier to read and debug % (2) use a block of code (the function) over and over again in same % main program or in multiple programs AND only have to make change in % one place if you want to make a change, NOT in multiple copies of code % my function myfun (arbitrary name) is in the file myfun.m in same % folder as this main program (or add location to Matlab path if elsewhere) a = 3 b = 5 c = myfun(a,b) % functions can take arrays as input and/or return % arrays as result when written to do so d = [1 3 4] e = [5 6 7] f = myfun(d,e) % FOR HOMEWORK, ADD LINE TO "TYPE" FUNCTION AT END OF EVERY CODE % SECTION THAT USES A FUNCTION YOU WROTE SO I CAN SEE YOUR WORK!!! type myfun.m a = 3 b = 5 c = 8 d = e = f = 5

8 function result = myfun(x,y) % myfun adds two input #'s or arrays % comments immediately after 1st line appear when enter help functionname result = x + y; % suppress output in func example 4 - image manipulation % WARNING: ADD SEMICOLON TO END OF LINE INVOLVING AN IMAGE ARRAY!!! % IF NOT YOU WILL WAIT AS ZILLIONS OF NUMBERS DISPLAY IN COMMAND WINDOW % if you leave ; off by mistake, click in command window and type % ctrl+c or ctrl+break on Windows OS, or command+period on Mac OS % read JPG image file and assign to a variable % easiest if JPG file in same folder as this main program im1 = imread('space.jpg'); % << NEED SEMICOLON OR GET LOTS OF NUMBERS!!! % use image() to display image in homework % image() shows rows & columns on axes to see correspondence to array % or can use imshow() as I did in class % image() more often used for computed images, imshow() for photos figure(1) imshow(im1) title('using imshow()','fontsize',18) figure(2) image(im1) title('using image() - NOTE ROW & COLUMN NUMBERS') % use size() to get rows, columns, pages of 3 (pages) of 2D arrays % use class() to get class (logical, char, integer, etc.) of values % images use unsigned integers stored in 8 bits, since 2^8 = 256 and % RGB color values can take values of 0 through 255 (256 values), % AND to save memory rather than using % default double-precision floating point (64 bits) % make a copy of im1 im2 = im1; % set some arbitrary range of values in im2 to another value im2(1000:1400,500:1500,3) = 0; figure(3) image(im2) 6

9 % set part of that range back to original im2(1100:1300,700:1000,3) = im1(1100:1300,700:1000,3); figure(4) image(im2) % ALSO SEE THESE LINKS AT % ReactorLab.net > Resources > Matlab > More notes % * Green screen animation in Matlab % * Pioneer of blue & green screening... Warning: Image is too big to fit on screen; displaying at 67% 7

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11 Published with MATLAB R2016a 9